1. Field of the Invention
The present invention relates to a recording medium suitable for use in ink jet recording, an ink jet recording method using the same and a printed product.
2. Description of the Prior Art
Conventional recording media used for ink jet recording include a recording sheet comprising an ink receiving layer consisting of acetal-modified polyvinyl alcohol, as disclosed in Japanese Patent Laid-Open Nos. 63-221077, 5-221112, 5-262028 and 7-1828; a recording sheet comprising an ink receiving layer consisting of polyvinyl alcohol and polyvinyl pyrrolidone, as disclosed in Japanese Patent Laid-Open No. 55-146786; a recording sheet comprising an ink receiving layer mainly consisting of polyvinyl pyrrolidone, as disclosed in Japanese-Patent Publication No. 3-29596; a recording sheet comprising an ink receiving layer consisting of polyvinyl alcohol and polyvinyl butyral, as disclosed in Japanese Patent Laid-Open No. 57-102391; a recording sheet comprising an ink receiving layer consisting of a crosslinked water-soluble resin, as disclosed in Japanese Patent Laid-Open No. 58-89391; a recording sheet having excellent resistance to fingerprint marks and comprising an ink receiving layer consisting of a polyester resin, as disclosed in Japanese Patent Laid-Open No. 5-309956; a recording sheet comprising an ink receiving layer provided on a polyester film and consisting of water-soluble polyvinyl alcohol having a degree of saponification of 70 to 90%, as disclosed in Japanese Patent Laid-Open No. 60-220750; a recording sheet comprising an ink receiving layer consisting of a water-soluble metallic salt with more than two valencies and a cationic organic material, as disclosed in Japanese Patent Laid-Open No. 60-67190; and a recording sheet comprising an ink receiving layer containing a polyallylamine derivative as a cationic resin, as disclosed in Japanese Patent Laid-Open No. 61-61887. In addition, Japanese Patent Laid-Open No. 7-40649 discloses a recording sheet having an ink receiving layer consisting of an active energy ray curable resin, and Japanese Patent Laid-Open No. 7-55581 discloses a recording sheet having polyoxyethylene as a skeleton and an ink receiving layer consisting of an active energy ray curable resin.
Recent improvements in the performance of ink jet recording apparatus, such as increased recording speed and realization of multicolor recording, have brought about the need for the ink jet recording medium to have a wide variety of high-performance characteristics.
Namely, the recording medium must simultaneously satisfy the following requirements:
(1) High ink absorbing power (high absorption capacity and high absorption speed);
(2) The ability to form dots with high optical density and clear peripheries;
(3) The ability to form substantially circular dots having smooth peripheries;
(4) Minimal change in printing characteristics and the prevention of curling due to changes in temperature and humidity;
(5) Anti-blocking property;
(6) Stability and the ability to stably maintain an image without deterioration in long-term storage (particularly, in an environment of high temperature and humidity);
(7) Resistance to fingerprint marks;
(8) Excellent water resistance of the ink receiving layer and the recording portion;
(9) Excellent adhesion between the ink receiving layer and the substrate; and
(10) Excellent coating properties of a coating solution for forming the ink receiving layer during the formation of the ink receiving layer.
Regarding the above-mentioned conventional recording media, the recording medium disclosed in Japanese Patent Publication No. 3-29596, which comprises an ink receiving layer mainly comprising polyvinyl pyrrolidone, has relatively good ink absorbing power at room temperature and normal humidity, but the ink dries very slowly at a high temperature and high humidity, thereby causing blocking. The recording medium also has the problem that the recording surface of the ink receiving layer has low mechanical strength and is thus easily damaged.
The recording medium disclosed in Japanese Patent Laid-Open No. 55-146786, which comprises an ink receiving layer comprising polyvinyl alcohol and polyvinyl pyrrolidone, has good ink absorption and fixing properties, but the recorded part and the ink receiving layer have poor water resistance.
The recording medium disclosed in Japanese Patent Laid-Open No. 57-102391, which comprises an ink receiving layer comprising polyvinyl alcohol and polyvinyl butyral, has the problem that the ink receiving layer has poor compatibility between the two resins.
The recording medium disclosed in Japanese Patent Laid-Open No. 60-220750, which comprises an ink receiving layer mainly comprising polyvinyl alcohol, is excellent in anti-blocking property and mechanical strength of the recording surface, but the recording medium has the problem that, when the recording medium is allowed to stand in an environment of high temperature and high humidity for a long time, it deteriorates, and the ink absorbing power deteriorates, and that, when an image is allowed to stand in an environment of high temperature and high humidity for a long time, the dots become blurred, and the image definition thus deteriorates.
The recording medium disclosed in Japanese Patent Laid-Open No. 58-89391, which comprises an ink receiving layer formed by crosslinking a water-soluble resin, is excellent in water resistance of the ink receiving layer, but it has poor ink absorption.
The recording medium disclosed in Japanese Patent Laid-Open No. 5-309956, which comprises an ink receiving layer mainly comprising a polyester resin, has excellent resistance to fingerprint marks, but it has other properties such as its ink receiving and long-term storage properties are very poor. Thus, the recording medium does not satisfy the above requirements.
The problems with respect to ink absorption and water resistance of the ink receiving layer can be solved to some extent by using polyvinyl acetal for forming the ink receiving layer, as disclosed in Japanese Patent Laid-Open Nos. 63-221077, 5-221112, 5-262028 and 7-1828. However, the image definition is not satisfactorily maintained, particularly when a recorded image is allowed to stand in an environment of high temperature and high humidity for a long time.
In addition, when the ink receiving layer is provided in a specified form on the recording medium, for example, when the ink receiving layer is provided on a plate-shaped substrate, a coating solution for forming the ink receiving layer flows to the circumference of the plate-shaped substrate, and thus must be printed in a pattern so as to prevent coating on the circumference of the plate-shaped substrate. Although a polyvinyl alcohol resin is solid and must be printed after being dissolved in some solvent, the resin has poor solubility to solvents, and thus has the problem of requiring a thick coating of the resultant resin solution because of the low solid content thereof. The resin solution also has poor leveling properties and anti-foaming properties, and thus has the problem of poor printing properties.
The recording medium disclosed in Japanese Patent Laid-Open Nos. 4-67986 and 4-320877, which comprises an ink receiving layer mainly comprising alumina hydrate, is satisfactory in ink absorption and anti-blocking property, but the water resistance of the ink receiving layer is insufficient because the binder component of the alumina hydrate is a water-soluble resin. The recording medium is also unsatisfactory in other properties, such as ink absorption capacity, curling, transparency and storage properties.
The ink receiving layer disclosed in Japanese Patent Laid-Open No. 7-40649, which is formed by using an active energy ray curable resin, has excellent water resistance and improved stability to changes in temperature and humidity, and the coating solution which forms the ink receiving layer has excellent printing properties. However, since the ink receiving layer has a high crosslink density, the ink receiving layer exhibits good ink jet printing properties in a recorded portion with a low printing duty, but the ink receiving layer cannot sufficiently absorb the ink applied to a recorded portion with a high printing duty and thus has the problem of causing color nonuniformity referred to as "beading" or bleeding at boundaries between adjacent different colors.
Like the ink receiving layer formed by using an active energy ray curable resin, the ink receiving layer disclosed in Japanese Patent Laid-Open No. 7-55581, which comprises polyoxyethylene as a skeleton and which is formed by using an active energy ray curable resin, cannot sufficiently absorb the ink applied to a recorded portion with a high printing duty, and thus has the problem of causing beading or bleeding at boundaries between different colors. The coating solution for forming the ink receiving layer also has poor coating properties for the substrate.
At present, the above-mentioned conventionally known techniques cannot produce a recording medium which simultaneously satisfies the above requirements,